Prognostic significance of the clinical and radiological haemorrhagic transformation subtypes in acute ischaemic stroke: A systematic review and meta‐analysis

Abstract Background and purpose The aim was to investigate the associations of haemorrhagic transformation (HT) and its clinical and radiological subtypes with functional outcome, mortality, early neurological deterioration (END) and neurological complications in patients with acute ischaemic stroke (AIS). Methods A systematic review and meta‐analysis of observational studies on the associations of overall HT, clinical HT subtypes (asymptomatic intracerebral haemorrhage [aICH] and symptomatic intracerebral haemorrhage [sICH]) or radiological HT subtypes (haemorrhagic infarction [HI‐1 or HI‐2] and parenchymal haemorrhage [PH‐1 or PH‐2]) with prognosis in patients with AIS was performed. PubMed, Web of Science and Embase were systematically searched. Random effects models were used to calculate pooled estimates. Results Fifty‐one studies with 100,510 patients were pooled in the meta‐analysis. Overall HT was associated with worse functional outcome (odds ratio [OR] 2.12, 95% confidence interval [CI] 1.55–2.90), increased mortality (OR 1.87, 95% CI 1.52–2.30), END (OR 2.35, 95% CI 1.46–3.77), early‐onset seizures (OR 2.58, 95% CI 1.63–4.10) and post‐stroke epilepsy (OR 2.23, 95% CI 1.11–4.49). For clinical subtypes, sICH remained significantly associated with the aforementioned poor prognoses except post‐stroke epilepsy, and aICH was associated with worse functional outcome but was unrelated to mortality. For radiological subtypes, PH (especially PH‐2) was strongly associated with poor prognosis. HI‐2 was associated with worse functional outcome, and HI‐1 was associated with a lower risk of mortality and END. Conclusions Regardless of whether AIS patients undergo thrombolysis or thrombectomy, overall HT, sICH and PH (especially PH‐2) are associated with a substantially increased risk of worse functional outcome, mortality, END or neurological complications. The presence of aICH is related to worse functional outcome but is independent of increased mortality. HI‐2 impairs functional independence, and HI‐1 does not cause neurological impairment.